α 2-Macroglobulin bait region integrity : Role in determining fast-form structure

Abstract

To determine whether integrity of the bait region affects the structure of the remainder of human α 2-macroglobulin (α 2M), we have determined the separation between cysteine residues in a methylamine-reacted fast-form of α 2 M. From reduction in fluorescence intensity of covalently-bound donor fluorophore caused by proximity to an acceptor, a separation of 35 ± 8 Å was calculated, which is identical to a previously determined value for proteinase-treated fast-form α 2M. This indicates that although bait region cleavage is the physiological route to conformational change in α 2M, bait region integrity per se does not significantly affect the structure of fast-form α 2M.